滚切剪剪切力影响因素的分析及有限元模拟

对滚切剪剪切原理进行了分析,得到了影响剪切力的5个主要因素,即钢板厚度、切入深度比、剪切速度、剪切角、剪刃间隙.借助于有限元分析软件ANSYS/LS-DYNA,获得了5个因素与剪切力的关系.这能为滚切剪的设计提供理论依据.     

机场压实填土抗剪强度的试验研究

采用原位直剪试验、室内中型直剪试验等测试手段,运用优定斜率法等数理统计方法,对机场高填方压实土的强度特性进行了分类研究,为场区设计方案的优化、稳定性评价与治理,提供了参数。该试验成果可供类似工程借鉴、参考。     

滚筒式飞剪机的剪切性能理论分析及有限元模拟

本文对现有的飞剪剪切力计算公式进行了归纳总结和理论分析,采用有限元法对滚筒式飞剪的剪切过程进行有限元数值模拟,并与理论计算结果进行对比与分析,结果表明剪切力的大小与钢板的厚度、宽度、速度和材料的强度极限有密切关系:钢板厚度每增加0.5 mm,剪切力增加25.2％;钢板宽度每增加150 mm,剪切力增加约12％;钢板运行速度每增加40 m/min,剪切力增加1.7％;板带材料强度极限越高,所需剪切力越大.     

四连杆曲柄式飞剪剪切力分析

在飞剪剪切过程中,剪切轧件所需的剪切功由传动系统释放的动能和电机做功提供。基于能量守恒定律,建立四连杆曲柄式飞剪机剪切力计算模型。通过与理论计算模型比较,剪切力的计算误差较小,证明该模型的有效性。借助本文给出的剪切力计算模型,对评估飞剪的工作状态、新产品开发有一定的参考价值。     

Mechanical strength test method for solder ball joint in BGA package

Ball shear tests were investigated in terms of effects of test parameters, i.e. shear height and shear speed, with an experimental and non-linear finite element analysis in order to evaluate the solder joint integrity of area array packages. The substrate was a common SMD type with solder bond pad openings of 460 μm in diameter. Microstructural investigations were carried out using SEM, and the IMCs were identified with EDS. It was observed that increasing shear height, at fixed shear speed, results in decreasing shear force, while the shear force increased with increasing shear speed at fixed shear height. Excessive shear height could cause some detrimental effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball surface. Low shear height conditions are favorable for screening the type of brittle interfacial fractures or degraded layers in the interfaces.     

Quantitative calculation of local shear deformation in adiabatic shear band for Ti-6Al-4V

JOHNSON-COOK（J-C） model was used to calculate flow shear stress-shear strain curve for Ti-6Al-4V in dynamic torsion test. The predicted curve was compared with experimental result. Gradient-dependent plasticity（GDP） was introduced into J-C model and GDP was involved in the measured flow shear stress-shear strain curve, respectively, to calculate the distribution of local total shear deformation（LTSD） in adiabatic shear band（ASB）. The predicted LTSDs at different flow shear stresses were compared with experimental measurements. J-C model can well predict the flow shear stress-shear strain curve in strain-hardening stage and in strain-softening stage where flow shear stress slowly decreases. Beyond the occurrence of ASB, with a decrease of flow shear stress, the increase of local plastic shear deformation in ASB is faster than the decrease of elastic shear deformation, leading to more and more apparent shear localization. According to the measured flow shear stress-shear strain curve and GDP, the calculated LTSDs in ASB are lower than experimental results. At earlier stage of ASB, though J-C model overestimates the flow shear stress at the same shear strain, the model can reasonably assess the LTSDs in ASB. According to the measured flow shear stress-shear strain curve and GDP, the calculated local plastic shear strains in ASB agree with experimental results except for the vicinity of shear fracture surface. In the strain-softening stage where flow shear stress sharply decreases, J-C model cannot be used. When flow shear stress decreases to a certain value, shear fracture takes place so that GDP cannot be used.     

Calculation of temperature distribution in adiabatic shear band based on gradient-dependent plasticity

A method for calculation of temperature distribution in adiabatic shear band is proposed in terms of gradient-dependent plasticity where the characteristic length describes the interactions and interplaying among microstructures. First, the increment of the plastic shear strain distribution in adiabatic shear band is obtained based on gradient-dependent plasticity. Then, the plastic work distribution is derived according to the current flow shear stress and the obtained increment of plastic shear strain distribution. In the light of the well-known assumption that 90% of plastic work is converted into the heat resulting in increase in temperature in adiabatic shear band, the increment of the temperature distribution is presented. Next, the average temperature increment in the shear band is calculated to compute the change in flow shear stress due to the thermal softening effect. After the actual flow shear stress considering the thermal softening effect is obtained according to the Johnson-Cook constitutive relation, the increment of the plastic shear strain distribution, the plastic work and the temperature in the next time step are recalculated until the total time is consumed. Summing the temperature distribution leads to rise in the total temperature distribution. The present calculated maximum temperature in adiabatic shear band in titanium agrees with the experimental observations. Moreover, the temperature profiles for different flow shear stresses are qualitatively consistent with experimental and numerical results. Effects of some related parameters on the temperature distribution are also predicted.     

温轧路径对钛/钢爆炸复合板抗剪切强度的影响

对爆炸复合的钛/钢复合板进行了一道次60%的温轧,研究了一道次温轧钛/钢爆炸复合板的近界面微观组织及剪切强度。结果显示,一道次温轧工艺可以引起钛层和钢层近界面组织的显著剪切变形。由于剪切变形,钛层形成了RD分散织构。钢层含有高组份的旋转立方织构及低组份的γ纤维织构。对比常规多道次轧制方法,由于剪切变形可细化界面化合物,使得一道次温轧钛/钢复合板抗剪切强度得到提升。     

圆盘剪主轴刚度分析及结构优化

中厚板圆盘剪剪切能力的不足严重制约了钢铁企业的中厚板精整的能力和质量。通过对剪切主轴进行受力分析,发现主轴和剪刃的刚度不足是制约剪切能力提高的主要因素。为此,建立了主轴系变形的简支梁计算模型,提出了把主轴剪切端的双列调心滚子轴承改为双列圆锥滚子轴承、减少剪刃的悬伸量,并在不改变主轴箱体尺寸的前提下适当增加轴径的解决方案。采用有限元计算模型对该方法进行了验证,实例分析显示,在剪切Q235厚30mm钢板时,优化后的主轴系剪刃间隙和重合度变化量只有优化前的约1/5和1/2,轴承的承载能力也完全满足需要。此方法在某钢厂中厚板圆盘剪改进中得到应用并取得很好效果,为同类圆盘剪的改进提供了理论基础和新的思路。     

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 对现有的剪断销剪切试验用重型单剪装置存在的问题进行了系统分析,提出了对该重型单剪装置结构优化的具体方案和实施办法。经分析计算证明,所提出的方案合理,该套装置应用于大型水电机组剪断销的剪切实验上能够产生预期的效果。     

新一代液压滚切剪技术的研究及应用

为提高中厚板的剪切质量,降低设备成本,提出了一种PR-8R-PR杆系的剪切机构,该机构将左右两台液压缸与机架铰接,液压缸推动连杆,使其带动机架运动,完成剪切。控制系统采用带检测反馈的双闭环控制,精度高,稳定性好。剪切后切口断面毛刺≤0.5mm,断面垂直度90°±1°,钢板边部瓢曲度≤0.15mm/m。     

钢—铝固液相复合中分形几何的研究与应用

研究了钢铝固液相复合板剪切撕裂表面的分形几何特征, 并且确定了分形维数与界面剪切强度之间的关系。研究结果表明： 剪切撕裂表面的分形维数与界面剪切强度之间满足ｙ ＝ ２６ ．２ ｘ ＋ ４ ．２ 。利用由直径为１ ．４ ～１ ．６ ｍ ｍ 的钢丝制成的钢丝轮对０８Ａｌ 钢板表面进行打毛处理, 可以得到最佳的钢板表面粗糙状态, 使得复合板界面剪切撕裂表面的分形维数最大约为２ ．３３ , 从而得到复合板的最大剪切强度为６５ ．３ ＭＰａ 。     

变规格过程中圆盘剪张力优化设定方法

针对变规格过程中圆盘剪张力设定值频繁突变,使控制系统不断发送调整信号,造成圆盘剪前后带钢实际张力的大幅波动,影响剪切稳定的实际问题,结合圆盘剪的设备及工艺特点,在首次引入张力设定值允许调整系数的基础上,提出了一套圆盘剪变规格过程中以稳定剪切为目标的张力设定方法,即通过预先计算变规格前后钢卷张力设定值的调整率来判断是否改变张力设定值,有效减少了张力设定值的调整次数,降低了剪切过程中实际张力值的波动率,提高了剪切稳定性,改善了圆盘剪的剪切质量,抑制了毛刺等缺陷的发生率。该技术投入现场应用后,效果良好,同时减少了下游用户的质量异议。     

提高铝挤压机主剪刀剪切效果方法研究

对铝挤压机主剪刀剪切过程受力进行了分析,介绍了不同铝挤压机主剪刀结构形式,提出了旋转式大型挤压机主剪刀结构,建立了旋转供油装置,提出了旋转式主剪刀剪切过程控制方法,应用重型运动部件惯性控制手段显著提高了主剪刀的运行速度。研究结果在120MN铝型材挤压机上得到了应用,结果表明:旋转式主剪刀可有效提高剪切效果。     

30万t横切生产线稀油润滑加热系统改造

首钢京唐公司30万t横切生产线稀油集中润滑系统在运行过程中,原套管式电加热器存在加热功率偏小与加热效果不良等问题,通过将原套管式加热器改造为管道式电加热器,同时优化了压力、温度、流量联锁控制,解决了该润滑系统加热器存在的突出问题.     

粘土湿型砂剪切变形功测试方法及其韧性评价

使用PLC控制的剪切变形功测试仪,记录型砂试样剪切变形过程的变形与强度变化,处理其结果得到剪切功,以表征型砂的韧性.研究了型砂紧实率、膨润土含量、制样锤击次数和淀粉加入量对试样剪切功的影响,并探讨剪切变形中不同阶段剪切功的意义.     

四连杆曲柄飞剪机剪切力测试与分析

通过对四连杆曲柄飞剪机剪切力的测试与分析,弄清了剪切力与工艺参数之间的定量关系,为合理安排生产,确保飞剪机安全运行,掌握飞剪机的最大生产能力,正确评估飞剪机的工作状态提供了重要依据。在测试中,解决了不少技术难题,如剪刃受力静不定系统的转化、剪刃的技术改造方法、标定时实际剪切状态的模拟、剪切力信号的获取方法、应力测量时的温度补偿与导线的热辐射防护等。     

滚筒机构螺旋剪刃飞剪机静态剪切力计算公式探讨

建立了滚筒式螺旋剪刃飞剪机剪切力计算的公式,并提出了有关见解。     

高线2号飞剪剪臂及进出口导钢装置的改进

针对高速线材2号飞剪、上下剪臂及前后导钢装置存在的问题,提出并实施了改进措施,较好解决了堆钢的问题,取得了提高作业率和成材率的良好效果。     

基于实测剪切应力及局部应变的Ti-6Al-4V绝热剪切带的峰值温度估算

认为试样表面的变形场出现不连续性不是绝热剪切带出现的标志,而是形变绝热剪切带进一步发展的结果;在计算绝热剪切带内部的峰值温度时应从局部剪切应变中扣除弹性应变,因为弹性应变不会对塑性功有所贡献。以动态扭转的Ti-6Al-4V试样（TA-50）为例,计算了绝热剪切带内部的峰值温度,其被划分为3部分：环境温度、均匀和非均匀变形引起的温度。在两种条件下（从局部剪切应变中扣除弹性应变与否）,计算出的峰值温度分别为669和665 ℃,其在热回复和再结晶的温度范围之内,未达到相变的温度,比Liao及Duffy的理论计算值（630 ℃）要高。如果剪切应力-局部塑性剪切应变的关系不能完全确定,适当的近似是必要的。